Open Water Sediment Dynamics on the Alaskan Beaufort Sea Shelf: A
Numerical Modeling Study
Abstract
Sediment dynamics on continental shelves can impact coastal
geomorphology, habitat suitability, and biogeochemical cycling. In the
coastal Arctic, for example, the rate at which sediment is transported
to locations where it can be sequestered impacts the fate of carbon from
thawing permafrost. To complement observational studies, this paper uses
a numerical model to better understand variability in shelf sediment
transport over timescales of hours to months. Specifically, a coupled
hydrodynamic – sediment transport model, the Regional Ocean Modeling
System (ROMS) - Community Sediment Transport Modeling System (CSTMS), is
implemented within the Coupled Ocean-Atmosphere-Wave-Sediment Transport
(COAWST) Modeling System, for the 2019 open water (nearly ice-free)
season on the Alaskan Beaufort Sea shelf. Results showed that wave- and
current-induced bed shear stresses frequently exceeded the critical
stress for erosion and caused resuspension. Waves dominated bed shear
stresses in depths shallower than 10 m and currents dominated in depths
deeper than 20 m. Suspended sediment concentrations were highest during
energetic wave events, although time periods with fast currents also
caused resuspension, especially on the mid-to-outer shelf. When averaged
over the open water season, modeled suspended sediment fluxes were
westward, despite prevailing eastward currents, because of events
characterized by fast westward currents. We expect these events may
become more important for future sediment fluxes as storm frequency is
projected to increase. Overall, the results improve our understanding of
how sediment dynamics vary on the Beaufort Sea shelf during the open
water season and provide insight into shelves characterized by strong
currents and wave-induced resuspension.